2.7. Sample treatment
Ten different herbal plant samples were used in this
investigation. The samples were harvested at different
locations within Ogbomoso town in September 2000.
The plants were authenticated by Mr. T.K. Odewo of
the Herbarium headquarter, Forestry Research Institute
of Nigeria (FRIN), Ibadan, where voucher specimens
were kept. The identities, as well as the medicinal properties,
of the plant samples under investigation are
shown seen in Table 1.
The samples were washed with deionized water and
allowed to dry in moisture extraction oven for 48 h at a
temperature of 65 C. The samples were then ground
with a Wiley mill for a time between 2 and 5 min and
sieved through a 0.5 mm diameter sieve supplied with
the mill. The pulverized and powdered plant samples
were stocked in paper sample bags inside desiccators
before analysis.
2.8. Digestion of the samples
The wet-ashing microwave-assisted method was
employed for the digestion procedure described below.
From 0.4 to 0.45 g of the powdered plant samples were
weighed into the Teflon PFA vessels and treated with 5
ml (2:1) of 69.4% w/w HNO3 and 70.0% w/w HCIO4.
The vessels was covered with a lid and screw cap; the
contents of each vessel were arranged in the turntable
and put into the microwave oven for digestion in a preselected
programme (one stage at 0% for 5 s; two stages